#!/usr/bin/python
# -*- coding: utf-8 -*-


class Node(object):
    def __init__(self, val, p=0):
        self.data = val
        self.next = p
        self.prev = p


class LinkList(object):
    def __init__(self):
        self.head = 0

    def __getitem__(self, key):
        if self.is_empty():
            print("linklist is empty")
            return
        elif key < 0 or key > self.getlength():
            print("the given key is error")
            return
        else:
            return self.getitem(key)

    def __setitem__(self, key, value):
        if self.is_empty():
            print('linklist is empty.')
            return
        elif key < 0 or key > self.getlength():
            print('the given key is error')
            return
        else:
            self.delete(key)
            return self.insert(key)

    def initlist(self, data):
        self.head = Node(data[0])
        p = self.head
        for i in data[1:]:
            node = Node(i)
            p.next = node
            node.prev = p
            p = p.next

    def getlength(self):
        p = self.head
        length = 0
        while p != 0:
            length += 1
            p = p.next
        return length

    def is_empty(self):
        if self.getlength() == 0:
            return True
        else:
            return False

    def clear(self):
        self.head = 0

    def append(self, item):
        q = Node(item)
        if self.head == 0:
            self.head = q
        else:
            p = self.head
            while p.next != 0:
                p = p.next
            p.next = q
            q.prev = p

    def getitem(self, index):
        if self.is_empty():
            print('Linklist is empty.')
            return
        j = 0
        p = self.head
        while p.next != 0 and j < index:
            p = p.next
            j += 1
        if j == index:
            return p.data
        else:
            print('target is not exist!')

    def insert(self, index, item):
        if self.is_empty() or index < 0 or index > self.getlength():
            print('Linklist is empty.')
            return
        if index == 0:
            q = Node(item, self.head)
            self.head = q
        p = self.head
        post = self.head
        j = 0
        while p.next != 0 and j < index:
            post = p
            p = p.next
            j += 1
        if index == j:
            q = Node(item, p)
            post.next = q
            q.prev = post
            q.next = p
            p.prev = q

    def delete(self, index):
        if self.is_empty() or index < 0 or index > self.getlength():
            print('Linklist is empty.')
            return
        if index == 0:
            q = Node(item, self.head)
            self.head = q
        p = self.head
        post = self.head
        j = 0
        while p.next != 0 and j < index:
            post = p
            p = p.next
            j += 1
        if index == j:
            post.next = p.next
            p.next.prev = post

    def index(self, value):
        if self.is_empty():
            print('Linklist is empty.')
            return
        p = self.head
        i = 0
        while p.next != 0 and not p.data == value:
            p = p.next
            i += 1
        if p.data == value:
            return i
        else:
            return -1


l = LinkList()
l.initlist([1, 2, 3, 4, 5])
print(l.getitem(4))
l.append(6)
print(l.getitem(5))
l.insert(4,40)
print(l.getitem(3))
print(l.getitem(4))
print(l.getitem(5))
l.delete(5)
print(l.getitem(5))
l.index(5)
